Logical Volumes - Partitions of tomorrow
Partitions, in the way they are commonly used, are not flexible. The solution is called Logical Volumes, managed with LVM, the Logical Volume Manager, and used with the Device-Mapper.
Recent distros, like Fedora or the coming EasyLFS 0.4, support using logical volumes, even as root-device.
But what's the big advantage of them?
One big advantage is that a logical volume is not bound to a certain device an the way a normal partition is. Like in a stripe-set (RAID 0) you can join devices into a volume-group. Inside that group you can create logical volumes, which can easily be resized. Of course you can also do that with a partition, GParted for example is a great tool for that. But the maximum size of a partition is limited by the size of the hard-disk, a logical volume can be as big as the volume-group, no matter if that consists of one partition or 10 complete hard-disks. Physical boundaries are no problem for logical volumes.
In addition to this you can easily adjust to your needs. You need more space? Buy another disk, add it to your volume-group and grow your logical volume. That's it! You can't do that without logical volumes. You'd have to use the new partition(s) seperately, on a new mountpoint.
Working with LVM is quite easy. On Linux.com you can find the article Pain-free disk space management with LVM which explains the basics of LVM. The interested reader might also have a look into the about LVM.
As said, I think logical volumes are a good thing to meet the growing disk-space-requirements and hope that more distros will offer the option to use them, Fedora 7, which I run on my notebook, even uses LVM by default.